Two senior House lawmakers said Tuesday that former national security adviser Michael Flynn may have violated the law by not disclosing payments for foreign work.

Republican Rep. Jason Chaffetz and Democratic Rep. Elijah Cummings –- the chairman and top Democrat, respectively, on the oversight committee – said classified military documents show Flynn did not ask permission or inform the government about payments he got for appearances before Russian organizations in 2015 and for lobbying that helped Turkey's government.

This raises concern whether Flynn violated a constitutional ban on foreign payments to retired military officers.

“The law requires him to seek permission … from the secretary of state and the Department of Defense,” Chaffetz said. “The response we’re getting [from those agencies] is there is no information, and that, we believe, is the potential violation.”

Chaffetz and Cummings said there was no evidence Flynn complied with federal law. They said Flynn could be criminally prosecuted, and they said Flynn should surrender the money he was paid.

"That money needs to be recovered," said Chaffetz. "You simply cannot take money from Russia, Turkey or anybody else."

Flynn got tens of thousands of dollars from Russian organizations after a trip there in 2015, and his consulting firm accepted $530,000 from a company tied to Turkey's government.

Flynn's lawyer said in a statement that Flynn disclosed the Russia trip, organized by the Russia Today news organization, in conversations with the Defense Intelligence Agency, where he was its former director.

"As has previously been reported, General Flynn briefed the Defense Intelligence Agency, a component agency of (the Defense Department), extensively regarding the RT speaking event trip both before and after the trip, and he answered any questions that were posed by DIA concerning the trip during those briefings," attorney Robert Kelner said.

Asked about the new concerns, White House Press Secretary Sean Spicer stressed Tuesday that “everything that is being questioned occurred prior to January 20.”

He would not comment directly on whether there was a violation, but maintained that the administration is cooperating with Congress’ requests, in response to criticism that the White House was not turning over all requested documents.

The House lawmakers spoke to reporters after members of the oversight committee were allowed to review classified documents relating to Flynn’s foreign contacts.

Flynn was forced out of the Trump administration after he allegedly misled Vice President Pence about past contacts with the Russian ambassador.

Fox News’ Catherine Herridge and The Associated Press contributed to this report.